Printer Friendly

Enzootic angiostrongyliasis in Shenzhen, China.

To the Editor: Angiostrongylus cantonensis is a zoonotic parasite that causes eosinophilic meningitis in humans after they ingest infective larvae in freshwater and terrestrial snails and slugs, paratenic hosts (such as freshwater fish, shrimps, frogs, and crabs), or contaminated vegetables. With the increase of income and living standards, and the pursuit of exotic and delicate foods, populations around the world have seen angiostrongyliasis become an important foodborne parasitic zoonosis (1-9).

Shenzhen municipality is situated in the most southern part of mainland People's Republic of China between the northern latitudes of 22[degrees]27' to 22[degrees]52' and eastern longitudes of 113[degrees]46' to 114[degrees]37'; it shares a border with the Hong Kong Special Administrative Region, China, in the south. The climate is subtropical, with an average annual temperature of 23.7 [degrees]C. The city is 1,952.84 [km.sup.2] and has a population of 10 million.

Since 2006, thirty-two sporadic cases of human eosinophilic meningitis caused by consumption of undercooked aquacultured snails have been documented in Shenzhen (Shenzhen Center for Disease Control and Prevention, unpub. data). To identify the source of these infections and assess the risk for an outbreak of eosinophilic meningitis, we conducted a survey to investigate whether A. cantonensis occurs in wild rats and snails in Shenzhen.

To examine A. cantonensis infection in intermediate host snails, 302 terrestrial snails (Achatina fulica) were collected from 10 investigation sites across Shenzhen, and 314 freshwater snails (Pomacea canaliculata) were sampled from 6 investigation sites. We examined the snails for A. cantonensis larvae by using pepsin digestion standardized procedures (3). To survey the prevalence of adult A. cantonensis in definitive host rats, we collected 187 Rattus norvegicus rats and 121 R. flavipectus rats collected from 4 sites where positive snails positive for A. cantonensis were found. These rats were examined for the presence of adult A. cantonensis in their cardiopulmonary systems.

A. cantonensis larvae were found in 96 (15.6%) of 616 examined snails. Of these, P. canaliculata had an average infection rate of 20.7% (65/314), significantly higher (p<0.01) than that of A. fulica (10.3%, 31/302), an indication that P. canaliculata may be the principal intermediate host for A. cantonensis in Shenzhen. A. cantonensis adults were recovered from the cardiopulmonary systems of 37 (12%) of 308 examined rats. Infection rate for R. norvegicus rats was 16.6% (31/187), significantly higher (p<0.01) than that for R. flavipectus (4.9%, 6/121), an indication that R. norvegicus may be the principal definitive host for A. cantonensis in Shenzhen, possibly due to the rat's preference for eating snails. Infection rates were higher for female rats (25.6% for R. norvegicus and 7.8% for R. flavipectus) than for male rats (8.9% for R. norvegicus, 2.9% for R. flavipectus), possibly because female rats eat more snails to supply proteins for reproduction. This report of enzootic A. cantonensis infection in wild rats and snails in Shenzhen demonstrates the existence of natural origins of infection with A. cantonensis for humans in this city.

Persons in Shenzhen eat raw or undercooked freshwater and terrestrial snails and slugs. This practice provides opportunities for infection with A. cantonensis, particularly given that P. canaliculata has been aquacultured intensively for human consumption. The prevalence of A. cantonensis in wild rats and snails in Shenzhen poses substantial risk for future outbreaks of human eosinophilic meningitis. Moreover, public health officials, epidemiologists, researchers, clinical technicians, medical practitioners, parasitologists, and veterinarians, as well as the general public, should be aware of such risks, and integrated strategies should be taken to reduce or eliminate such risks.


We thank Alasdair Nisbet for his assistance in improving the manuscript.

Project support was provided in part by a grant from Shenzhen Municipal Bureau of Science and Technology (grant no. 2007079) to R.-L.Z. and a grant from the Program for Changjiang Scholars and Innovative Research Team in University (grant no. IRT0723) to X.-Q.Z.


(1.) Alicata JE. The discovery of Angiostrongylus cantonensis as a cause of human eosinophilic meningitis. Parasitol Today. 1991;7:151-3. DOI: 10.1016/0169-4758-(91)90285-V

(2.) Hochberg NS, Park SY, Blackburn BG, Sejvar JJ, Gaynor K, Chung H, et al. Distribution of eosinophilic meningitis cases attributable to Angiostrongylus cantonensis, Hawaii. Emerg Infect Dis. 2007;13:1675-80.

(3.) Lindo JF, Waugh C, Hall J, Cunningham- Myrie C, Ashley D, Eberhard ML, et al. Enzootic Angiostrongylus cantonensis in rats and snails after an outbreak of human eosinophilic meningitis, Jamaica. Emerg Infect Dis. 2002;8:324-6.

(4.) Slom TJ, Cortese MM, Gerber SL, Jonse RC, Holtz TH, Lopez AS, et al. An outbreak of eosinophilic meningitis caused by Angiostrongylus cantonensis in travelers returning from the Caribbean. N Engl J Med. 2002;346:668-75. DOI: 10.1056/ NEJMoa012462

(5.) Leone S, De Marco M, Ghirga P, Nicastri E, Esposito M, Narciso P. Eosinophilic meningitis in a returned traveler from Santo Domingo: case report and review. J Travel Med. 2007;14:407-10. DOI: 10.1111/j.1708-8305.2007.00152.x

(6.) Tsai HC, Liu YC, Kunin CM, Lai PH, Lee SS, Chen YS, et al. Eosinophilic meningitis caused by Angiostrongylus cantonensis associated with eating raw snails: correlation of brain magnetic resonance imaging scans with clinical findings. Am J Trop Med Hyg. 2003;68:281-5.

(7.) Waugh CA, Shafir S, Wise M, Robinson RD, Eberhard ML, Lindo JF. Human Angiostrongylus cantonensis, Jamaica. Emerg Infect Dis. 2005;11:1977-8.

(8.) Lv S, Zhang Y, Steinmann P, Zhou XN. Emerging angiostrongyliasis in Mainland China. Emerg Infect Dis. 2008;14:161-4. DOI: 10.3201/eid1401.061529

(9.) Zhou P, Chen N, Zhang RL, Lin RQ, Zhu XQ. Food-borne parasitic zoonoses in China: perspective for control. Trends Parasitol. 2008;24:190-6. DOI: 10.1016/j. pt.2008.01.001

Author affiliations: Shenzhen Center for Disease Control and Prevention, Shenzhen, People's Republic of China (R.-L. Zhang, M.-X. Chen, S.-T. Gao, Y.-J. Geng, D.-N. Huang, J.-P. Liu, Y.-L. Wu); and South China Agricultural University, Guangzhou, People's Republic of China (M.-X. Chen, X.-Q. Zhu)

DOI: 10.3201/eid1412.080695

Address for correspondence: Xing-Quan Zhu, Laboratory of Parasitology, College of Veterinary Medicine, South China Agricultural University, 483 Wushan St, Tianhe District, Guangzhou, Guangdong Province 510642, People's Republic of China; email:
COPYRIGHT 2008 U.S. National Center for Infectious Diseases
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2008 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:LETTERS
Author:Zhang, Ren-Li; Chen, Mu-Xin; Gao, Shi-Tong; Geng, Yi-Jie; Huang, Da-Na; Liu, Jian-Ping; Wu, Yuan-Lia
Publication:Emerging Infectious Diseases
Article Type:Report
Geographic Code:9CHIN
Date:Dec 1, 2008
Previous Article:Molecular detection of Ehrlichia chaffeensis in Amblyomma parvum ticks, Argentina.
Next Article:Knowledge about avian influenza, European region.

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters